Magnetoresistive sensor having a closed domain structure and electrode biasing

Abstract

A magnetoelectric conversion element comprises a magnetoresistive effect material having a closed domain structure, a pair of contacts for supply of current flowing through the magnetoresistive effect material, and a bias electrode disposed between the contacts for biasing the direction of the current flow. The bias electrode is disposed so that the respective angles of intersection between the directions of current flow through different magnetic domains of the magnetoresistive effect material biased by the bias electrode and the directions of spontaneous magnetization biased by an external magnetic field are both increased or decreased.

What is claimed is: 
     
       1. A magnetoelectric conversion element comprising: a magnetoresistive effect material having a closed domain structure including first and second magnetic domains which are disposed in at least a part of said magnetoresistive effect material in its longitudinal direction and which have their directions of spontaneous magnetization reverse to each other in the longitudinal direction of said magnetoresistive effect material and third and fourth magnetic domains which are respectively positioned at opposite ends of said first and second magnetic domains to couple said first and second magnetic domains therethrough;   a pair of contacts for connection to a current source and formed on said magnetoresistive effect material in spaced relation from each other in the longitudinal direction of said magnetoresistive effect material; and   bias electrode means including at least one first segment disposed on said first magnetic domain to extend in a first direction inclined with respect to the longitudinal direction of said magnetoresistive effect material and at least one second segment disposed on said second magnetic domain to extend in a second direction inclined with respect to the longitudinal direction of said magnetoresistive effect material but opposite to said first direction, thereby biasing the direction of current flow through said magnetoresistive effect material between said pair of contacts with respect to the longitudinal direction of said magnetoresistive effect material.   
     
     
       2. A magnetoelectric conversion element according to claim 1, wherein said first and second segments of said bias electrode means are inclined with respect to the longitudinal direction of said magnetoresistive effect material so that the respective angles of intersection between the directions of current flow biased in said first and second magnetic domains by said first and second bias electrode segments and the directions of spontaneous magnetization biased in said first and second magnetic domations by an external magnetic field are both increased or decreased. 
     
     
       3. A magnetoelectric conversion element according to claim 2, wherein each of said pair of contacts has respective periphery portions facing said first and second bias electrode segments and inclined with respect to the longitudinal direction of said magnetoresistive effect material like said first and second bias electrode segments. 
     
     
       4. A magnetoelectric conversion element according to claim 3, wherein said first and second bias electrode segments are integral. 
     
     
       5. A magnetoelectric conversion element according to claim 2, wherein at least one groove is formed in said magnetoresistive effect material between said first and second magnetic domains to extend along the longitudinal direction of said magnetoresistive effect material. 
     
     
       6. A magnetoelectric conversion element according to claim 5, wherein each of said pair of contacts has periphery portions facing said first and second bias electrode segments and inclined with respect to the longitudinal direction of said magnetoresistive effect material like said first and second bias electrode segments, respectively. 
     
     
       7. A magnetoelectric conversion element comprising: a magnetoresistive effect material having at least two sections adjacent to each other along the longitudinal direction of said magnetoresistive effect material to provide closed domain structures, respectively, each of the magnetoresistive effect material sections including first and second magnetic domains which have their directions of spontaneous magnetization reverse to each other in the longitudinal direction of said magnetoresistive material and third and fourth magnetic domains which are respectively positioned at opposite ends of said first and second magnetic domains to couple said first and second magnetic domains therethrough;   a first contact for connection to a current source and formed on the third and fourth magnetic domains of and adjacent to each other between the adjacent magnetoresistive effect material sections;   second and third contacts for connection to a current source and formed respectively on the fourth and third magnetic domains of and spaced from each other between the outer magnetoresistive effect material sections; and   bias electrode means disposed on the magnetoresistive effect material sections, respectively, each of said bias electrode means including at least one first segment disposed on the first magnetic domain to extend in a first direction inclined with respect to the longitudinal direction of the magnetoresistive effect material and at least one second segment disposed on the second magnetic domain to extend in a second direction inclined with respect to the longitudinal direction of the magnetoresistive effect material but opposite to said first direction, thereby biasing the direction of current flow through the associated magnetoresistive effect material section between the contacts with respect to the longitudinal direction of the magnetoresistive effect material.   
     
     
       8. A magnetoelectric conversion element according to claim 7, wherein the first and second segments of each of said bias electrode means are inclined with respect to the longitudinal direction of the magnetoresistive effect material so that the respective angles of intersection between the directions of current flow biased in the first and second magnetic domains of the associated magnetoresistive effect material section by the first and second bias electrode segments and the directions of spontaneous magnetization biased in the first and second magnetic domations by an external magnetic field are both increased or decreased. 
     
     
       9. A magnetoelectric conversion element according to claim 8, wherein each of said first, second and third contacts has respective periphery portions facing the first and second bias electrode segments and inclined with respect to the longitudinal direction of the magnetoresistive effect material like the first and second bias electrode segments. 
     
     
       10. A magnetoelectric conversion element according to claim 9, wherein a groove is formed in each of the magnetoresistive effect material sections between the first and second magnetic domains thereof to extend along the longitudinal direction of the magnetoresistive effect material, and a pair of notches are formed at the boundary between the adjacent magnetoresistive effect material sections and opposite to each other in a direction perpendicular to the longitudinal direction of the magnetoresistive effect material. 
     
     
       11. A magnetoelectric conversion element comprising: a magnetoresistive effect material having a closed domain structure including first and second magnetic domains which have their directions of spontaneous magnetization reverse to each other in the longitudinal direction of said magnetoresistive effect material and third and fourth magnetic domains which are respectively positioned at opposite ends of said first and second magnetic domains to magnetically couple said first and second magnetic domains therethrough, a groove being provided between said first and second magnetic domains along the longitudinal direction of said magnetoresistive effect material to extend across said fourth magnetic domain so that said groove is opened at one end of the longitudinal direction of said magnetoresistive effect material to separate said fourth magnetic domain into two parts;   a connecting member of magnetic material formed through an electrically insulative member on and over both the two parts of said fourth magnetic domain separated by said groove;   first and second contacts for connection to a current source and formed respectively on said first and second magnetic domains at the ends thereof near said fourth magnetic domain;   a third contact formed on said third magnetic domain; and   bias electrode means including at least one first segment disposed on said first magnetic domain to extend in a first direction inclined with respect to the longitudinal direction of said magnetoresistive effect material and at least one second segment disposed on said second magnetic domain to extend in a direction inclined with respect to the longitudinal direction of said magnetoresistive effect material but opposite to said first direction, thereby biasing the direction of current flow through said magnetoresistive effect material between the contacts with respect to the longitudinal direction of said magnetoresistive effect material.   
     
     
       12. A magnetoelectric conversion element according to claim 11, wherein said first and second segments of said bias electrode means are inclined with respect to the longitudinal direction of said magnetoresistive effect material so that the respective angles of intersection between the directions of the current flow biased in said first and second magnetic domains by said first and second bias electrode segments and the directions of spontaneous magnetization biased in said first and second magnetic domations by an external magnetic field are both increased or decreased. 
     
     
       13. A magnetoelectric conversion element according to claim 12, wherein said first and second contacts have peripheral portions facing said first and second bias electrode segments and inclined with respect to the longitudinal direction of said magnetoresistive effect material likewise said first and second bias electrode segments, respectively, and said third contact has respective peripheral portions facing said first and second bias electrode segments and inclined with respect to the longitudinal direction of said magnetoresistive effect material likewise said first and second bias electrode segments.